HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Rózanowska, M. Articles by Sarna, T. Search for Related Content PubMed PubMed Citation Articles by Rózanowska, M. Articles by Sarna, T.

Photoreactivity of Aged Human RPE Melanosomes: A Comparison with Lipofuscin

Magorzata Róanowska¹, Witold Korytowski¹, Bartosz Róanowski², Christine Skumatz³, Mike E. Boulton⁴, Janice M. Burke³ and Tadeusz Sarna¹

¹ From the Department of Biophysics, Institute of Molecular Biology, Jagiellonian University, Kraków, Poland; the ² Department of Cytology and Genetics, Institute of Biology, Pedagogical Academy, Kraków, Poland; the ³ Departments of Ophthalmology and Cellular Biology, Neurobiology, and Anatomy, Medical College of Wisconsin, Milwaukee, Wisconsin; and the ⁴ Department of Optometry and Vision Sciences, Cardiff University, Cardiff, Wales, United Kingdom.

PURPOSE. To determine whether aging is accompanied by changes in aerobic photoreactivity of retinal pigment epithelial (RPE) melanosomes isolated from human donors of different ages, and to compare the photoreactivity of aged melanosomes with that of RPE lipofuscin.

METHODS. Human RPE pigment granules were isolated from RPE cells pooled into groups according to the age of the donors. Photoreactivity was determined by blue-light-induced oxygen uptake and photogeneration of reactive oxygen species. Short-lived radical intermediates were detected by spin-trapping, hydrogen peroxide by an oxidase electrode, singlet oxygen by cholesterol assay, and lipid hydroperoxides by iodometric assay.

RESULTS. Blue-light photoexcitation of melanosomes resulted in age-related increases in both oxygen uptake and the accumulation of superoxide anion spin adducts. The efficiencies of these processes, however, were still significantly lower than that induced by photoexcited lipofuscin. During irradiation of melanosomes, a substantial amount of oxygen was converted into hydrogen peroxide, whereas for lipofuscin, hydrogen peroxide accounted for not more than 3% of oxygen consumed. In contrast to lipofuscin, photoexcited melanosomes did not substantially increase the rate of oxidative reactions in the presence of polyunsaturated lipids or albumin. However, oxygen uptake was significantly elevated in the presence of ascorbate. Thus, the rate of photo-induced oxygen uptake in samples containing both ascorbate and melanosomes approached that observed in lipofuscin samples.

CONCLUSIONS. Blue-light-induced photoreactivity of melanosomes increases with age, perhaps providing a source of reactive oxygen species and leading to depletion of vital cellular reductants, which, together with lipofuscin, may contribute to cellular dysfunction.

This article has been cited by other articles:

				B. Rozanowski, J. M. Burke, M. E. Boulton, T. Sarna, and M. Rozanowska Human RPE Melanosomes Protect from Photosensitized and Iron-Mediated Oxidation but Become Pro-oxidant in the Presence of Iron upon Photodegradation Invest. Ophthalmol. Vis. Sci., July 1, 2008; 49(7): 2838 - 2847. [Abstract] [Full Text] [PDF]

				B.-L. L. Seagle, E. M. Gasyna, W. F. Mieler, and J. R. Norris Jr. Photoprotection of human retinal pigment epithelium cells against blue light-induced apoptosis by melanin free radicals from Sepia officinalis PNAS, November 7, 2006; 103(45): 16644 - 16648. [Abstract] [Full Text] [PDF]

				O. Strauss The Retinal Pigment Epithelium in Visual Function Physiol Rev, July 1, 2005; 85(3): 845 - 881. [Abstract] [Full Text] [PDF]

				B.-L. L. Seagle, K. A. Rezai, Y. Kobori, E. M. Gasyna, K. A. Rezaei, and J. R. Norris Jr. Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis PNAS, June 21, 2005; 102(25): 8978 - 8983. [Abstract] [Full Text] [PDF]

				M. Rozanowska, A. Pawlak, B. Rozanowski, C. Skumatz, M. Zareba, M. E. Boulton, J. M. Burke, T. Sarna, and J. D. Simon Age-Related Changes in the Photoreactivity of Retinal Lipofuscin Granules: Role of Chloroform-Insoluble Components Invest. Ophthalmol. Vis. Sci., April 1, 2004; 45(4): 1052 - 1060. [Abstract] [Full Text] [PDF]

				M A Mainster and J R Sparrow How much blue light should an IOL transmit? Br. J. Ophthalmol., December 1, 2003; 87(12): 1523 - 1529. [Abstract] [Full Text] [PDF]